Last night, Usui Nagisa had been running simulations the entire time. Lying on his bed, staring up at the ceiling, he mentally lined up the names that might be written next to his own on the pairing chart. Okajima. Maehara. Isogai. Twenty-seven possible patterns. Of those, only one was a combination he absolutely didn't want. The probability was one in twenty-seven. Low. Completely low. Nagisa kept telling himself that as he greeted the morning without sleep. --- Tuesday morning homeroom. The old school building of Class E swayed with the mountain-top wind rattling its windows, as always. Walls of wood that had stood for over forty years, floorboards that creaked, yesterday's chalk marks faintly remaining on the edge of the blackboard. That was the daily reality of Class E. Twenty-eight students gathered in a classroom tasked with assassinating Koro-sensei. Officially a remedial class, in reality a training ground classified at the national security level. And today, one whiteboard was added to that routine. Tentacles moving at Mach 20 plastered the whiteboard against the blackboard in an instant. Koro-sensei's movements were too fast to follow with the eye. By the time you noticed, it was already there. A sheet of paper labeled "Pairing Chart" at the top was pinned perfectly in place. "Alright, starting today, assassination training will transition to pair-based operations♪" The yellow face smiled brightly. That complexion was the same vivid yellow as this morning—the color of a good mood. The tips of the tentacles twitched in small, rapid movements. A sign that the sensors were fully activated. That movement that picked up every heartbeat fluctuation of humans within a thirty-meter radius. The classroom stirred. Nagisa closed his eyes the moment the chart was posted. A deep breath. Calm down, calm down. The probability is one in twenty-seven. It's fine. Completely fine— He opened his eyes. Mid-section of the whiteboard, left side. Next to the characters "Usui Nagisa," it read "Akabane Karma." Nagisa froze. "Whoa, Nagisa and Karma?" "Yeah, that's gonna be rough." "Why?" "Just a feeling." The classroom stirred again. Nagisa couldn't tear his eyes from the whiteboard, acutely aware of his heart rate climbing rapidly. All that simulation last night was useless. The practice he'd done three times to calm his pulse using an application of his concealment-of-presence skill—the one that had failed three times—was happening again now. "Huh." A languid voice came from the seat next to him. Akabane Karma was completely leaning back in his chair, looking at the chart with an air of indifference. His red hair was slightly disheveled. His uniform shirt was loose again today. Only the corner of his mouth lifted slightly. "So I'm paired with you." It was a teasing tone. The usual one. But Nagisa's observational ability caught something beneath that voice. His eyes. Karma's eyes weren't smiling. His mouth was shaped like a smile, but his gaze was oddly serious. It returned to his usual lazy expression in less than a second, but Nagisa had definitely seen it. (Why... would he make that face?) The moment he thought it, his chest jumped. It was the instant proof that last night's rooftop pulse-control training had been completely wasted. --- Until afternoon training, Nagisa spent the entire class period thinking about "how to calm down." No answer came. The forest behind the old school building was thick with May's greenery. Dappled sunlight fell in places, and fallen leaves on the ground were slightly damp. The training grounds in the back mountain used for Class E's assassination training—a forest area spreading behind this old school building, a twenty-minute climb up the mountain path from the main campus. Targets and obstacles were set up between the trees, and students honed their actual assassination techniques here. Today was the first pair-training session. They were supposed to attempt a pincer strategy combining Nagisa's concealment-of-presence with Karma's hand-to-hand combat ability. Supposed to, but the problem had already begun at the strategy meeting stage. The two crouched in the shadow of a thick tree trunk. Karma drew a simple diagram on the ground with a small branch, lowering his voice. "I'll come out from this side to draw the teacher's attention. While I do, you approach from the blind spot—" At that point, Karma leaned his face close to Nagisa's ear. He switched to a whisper. "—from here, and use the knife—" Nagisa froze. Close. His ear felt slightly warm. Because Karma's voice had become lower, it was all the more audible. His mind issued the command "listen to the strategy," but his ears weren't obeying at all. "...Yeah." That was all he managed to squeeze out in response. Karma pulled back slightly and glanced at Nagisa's face sideways. He said nothing. He activated concealment-of-presence. Close his eyes, steady his breathing, thin out his presence. In assassination, Nagisa's greatest weapon was this concealment-of-presence ability. A natural talent for slipping into the target's blind spot of awareness. But today— His heart pounded. (This is no good. Completely no good.) Karma's voice from moments ago was replaying in his head. The lowered voice, the close distance, the sensation of breath near his ear. All of it became noise, and instead of erasing his presence, it felt like his presence was increasing. That was the moment. "My, Nagisa's presence seems rather lively today." The yellow sphere poked its face out from behind the tree, aiming a tentacle tip directly at Nagisa. The teacher's tentacle sensors could see every heartbeat fluctuation. He couldn't hide it. Couldn't hide it at all. A tentacle flicked Nagisa's knife away. The anti-teacher knife—a special blade made of material that reacted only to Koro-sensei's cells—fell uselessly to the ground. In that instant, Karma dove in from the front. The timing was perfect. But Nagisa had no cover. Three of the teacher's tentacles gently restrained Karma's wrists. "So close, Akabane. You were just one person away." The teacher said it with a beaming smile, his complexion still that vivid yellow. Not shaken at all. The first pair-training session ended abruptly, anticlimactically. Karma stood up and glanced at Nagisa. His expression was unreadable. --- "Your coordination is lacking, you two." After school. The teacher said it with a smile. One tentacle perked up cheerfully. "Discuss your improvements on the rooftop♪" Then he vanished at Mach 20. All that remained was the lingering echo of "♪" and the two of them alone in the classroom. Nagisa couldn't move for several seconds. (The teacher definitely knows.) He knows, and he's doing this anyway. That's the kind of teacher he is. Koro-sensei possesses love-detection ability. Heart rate fluctuation, body temperature rise, pheromone concentration. Self-proclaimed 99.7% detection accuracy. And that's not all—he keeps personal files on every student in the staff room and maintains detailed "interpersonal relationship maps." The unwritten rule of Class E—if your romance is discovered by Koro-sensei, your love compatibility rating gets publicly analyzed on the blackboard—was born from that. Putting the two parties alone together for "improvement guidance" was one such tactic. In other words, right now, this was improvement guidance. Nagisa took a deep breath and headed out to the hallway first. --- The rooftop of the old school building had no railing. When he stepped out onto the flat roof section, mountains and mixed woodland spread around him. The sunset was beginning to catch on the mountain ridge. Orange and pale purple mixed in the wide sky. About sixty square meters of roof, just the two of them. Karma stood near the edge. Right at the edge where there was no railing. Nagisa wondered every time if he wasn't scared. But he'd never said it aloud. Karma turned toward him. The sunset was backlighting him, making his expression hard to see. "Hey." His voice was quiet. Not a teasing tone. "When you're paired with me, aren't you putting in weird effort?" Something tightened in Nagisa's chest. "...I'm not." "But your heart's fluttering like crazy. Enough to give away your position to Koro-sensei." "It's the tension of assassination." Karma paused for a beat. "...That's the same excuse you gave on the first evaluation." Nagisa's mouth stopped for a moment. That was true. When the teacher had pointed out his heart rate that day, Nagisa had said the same thing. That the tension of assassination was just increasing. He searched for a new excuse. Quickly. "I'm not feeling well today..." "You were eating lunch normally though." "The air in the forest is thin..." "Class E's forest hasn't changed elevation." "There were wasps flying nearby..." Karma went quiet for a moment. "...I didn't see any wasps though." He said it flatly. No emotion in the tone of denial. That, paradoxically, was what pierced Nagisa. Three excuses in a row, three quiet denials in a row. A graveyard of excuses was piling up before his eyes. Nagisa closed his mouth. He couldn't say anything. He couldn't find words for the truth. Even if he found them, he didn't know if he could say them. It had always been like this since childhood. He'd never practiced putting his feelings into words. Somewhere along the way, he'd stopped finding meaning in expressing emotion. Silence fell. The evening wind blew. Karma's red hair swayed slightly. Nagisa tried to meet Karma's eyes. They were blurred by the backlighting, but one thing was clear. Karma's eyes weren't smiling at all. No matter what shape his mouth made, his eyes said something different. Nagisa had seen that twice today. At homeroom this morning, and here now. Nagisa couldn't read what Karma was thinking. He was good at reading others' emotions, but this—he couldn't read it. The moment he thought he might be able to, his own heart rate got in the way. "———You two should head home soon, it's past dismissal time～" A yellow shadow passed across the roof at Mach 20. Gone in an instant. Just leaving behind the dismissal announcement. The discussion of improvements never progressed, and it ended. --- Coming down the mountain path, passing through the main campus, they reached the fork in the road. Nagisa's way home was toward the bus stop. Karma's way was toward the station. Kunutsugaoka Station, eight minutes on foot from the apartment "Maison Hillcrest"—Nagisa knew that place. He'd visited once during an assassination planning meeting. Karma had said his parents were often away due to work. That he spent a lot of time alone. Karma stopped at the fork. "See you." That was all he said before walking toward the station. Nagisa watched his back. "Karma." He called out his name. The words had come out. Karma turned around. The words caught in Nagisa's mouth. There was something he wanted to say. Something. But he didn't know what. Even if he knew, he couldn't put it into words. Even if he could put it into words, he didn't know if he could say it— "...Let's do our best in tomorrow's training." That was all that came out. Bland, meaningless words. Karma was silent for a moment. A pause like he was waiting for something. One second or two, it felt long to Nagisa. "Yeah, let's do that." That was all he said before walking again. This time he didn't look back. Nagisa watched his back grow distant. Walking alone down the residential street in the twilight. There was no one waiting at Karma's apartment. The back heading toward that destination led to an empty room. The thought made something ache deep in Nagisa's throat. He started walking toward the bus stop. Today's events kept circling in his head. Three excuses in a row, three quiet denials in a row. Karma's eyes on the rooftop—eyes that weren't smiling. That one moment when Karma